TOKYO — Japan condemned with outrage and horror on Sunday an online video that purported to show an Islamic State group militant beheading Japanese journalist Kenji Goto.
The video posted on militant websites late Saturday Middle East time ended days of negotiations to save the man and heightened fears for the life of a Jordanian fighter pilot also held hostage.
"I feel indignation over this immoral and heinous act of terrorism," Prime Minister Shinzo Abe told reporters after convening an emergency Cabinet meeting.
"When I think of the grief of his family, I am left speechless," he said. "The government has been doing its utmost in responding to win his release, and we are filled with deep regret."
He vowed that Japan will not give in to terrorism and will continue to provide humanitarian aid to countries fighting the Islamic State extremists.
The White House released a statement in which President Barack Obama also condemned "the heinous murder" and praised Goto's reporting, saying he "courageously sought to convey the plight of the Syrian people to the outside world."
Obama applauded Japan's "steadfast commitment to advancing peace and prosperity in the Middle East and globally, including its generous assistance for innocent people affected by the conflicts in the region."
"I was hoping Kenji would come back alive to thank everyone who had supported him," Goto's brother Junichi told Japanese public broadcaster NHK TV. "I am filled with sadness he couldn't do it."
Goto's mother, Junko Ishido, told NHK TV her son's death showed he was a kind, gentle man, trying to save another hostage. That hostage, Haruna Yukawa, was shown as purportedly killed in an earlier video.
The fates of Goto, a 47-year-old freelance journalist, and the Jordanian pilot, Lt. Muath Kaseasbeh, had been linked by the militants, but Saturday's video made no mention of the airman. Jordan's government spokesman, Mohammed al-Momani, declined comment. Earlier this week, Jordan had offered to free an al-Qaida prisoner for the pilot, but a swap never moved forward.
Saturday's video, highlighted by militant sympathizers on social media sites, bore the symbol of the Islamic State group's al-Furqan media arm.
Though the video could not be immediately independently verified by The Associated Press, it conformed to other beheading videos released by the extremists, who now control about a third of both Syria and neighboring Iraq in a self-declared caliphate.
The video, called "A Message to the Government of Japan," featured a man who looked and sounded like a militant with a British accent who has taken part in other beheading videos by the Islamic State group. Goto, kneeling in an orange prison jumpsuit, said nothing in the roughly one-minute-long video.
"Abe," the militant says in the video, referring to the Japanese prime minister, "because of your reckless decision to take part in an unwinnable war, this knife will not only slaughter Kenji, but will also carry on and cause carnage wherever your people are found. So let the nightmare for Japan begin."
Officials in Japan and the U.S. said they were trying to confirm the authenticity of the video.
"We have seen the video purporting to show that Japanese citizen Kenji Goto has been murdered by the terrorist group ISIL," said Bernadette Meehan, a spokeswoman for the White House's National Security Council, using an alternate acronym for the extremist group. "The United States strongly condemns ISIL's actions and we call for the immediate release of all the remaining hostages. We stand in solidarity with our ally Japan."
In Tokyo, Goto's friend Hiromasa Nakai said he was still hoping that the video was not authentic.
"I only can say I'm hoping this is not true," he said.
Goto was captured after he traveled to Syria in October to try to win Yukawa's release from the Islamic State group.
Yukawa reportedly was killed previously, though authorities have yet to authenticate the video claiming that.
The Jordanian pilot was captured after his fighter plane went down in December over an Islamic State-controlled area of Syria.
Earlier this week, Jordan had offered to release an al-Qaida prisoner for the pilot. However, in a purported online message earlier this week, the militants threatened to kill the pilot if the prisoner wasn't released by Thursday. That deadline passed, and the families of the pilot and the journalist were left waiting in agony.
Late Friday, Japan's deputy foreign minister reported a deadlock in efforts to free Goto. Jordan and Japan had reportedly conducted indirect negotiations with the militants through Iraqi tribal leaders.
The hostage drama began last week after militants threatened to kill Goto and Yukawa in 72 hours unless Japan paid $200 million.
Later, the militants' demand shifted to seeking the release of the al-Qaida prisoner, Sajijda al-Rishawi, 44, who faces death by hanging in Jordan for her role in triple hotel bombings in Amman in 2005. Sixty people were killed in those attacks, the worst terror attack in Jordan's history.
Al-Rishawi has close family ties to the Iraq branch of al-Qaida, a precursor of the Islamic State group.
Associated Press writers Jon Gambrell in Cairo, Karin Laub in Amman, Jordan, and Kaori Hitomi in Tokyo contributed to this report.